Backfire circuit breaker



June 28, 1949. D. L. MHLLER 2,474,487

BACKFIRE CIRCUIT BREAKER Filed June 10, 1947 2 Sheets-Sheet 1 INVENTOR.

ZLbnaUUCMZZe/ A ORA/ WITNESS June 28, 1949. D. MILLER BACKFIRE CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed June 10, 194'? z9a O we I A OgNEY INVENTOR. @mald4772dler BY WITNESS: m.

Patented June 28, 1949 BACKFIRE CIRCUIT BREAKER Donald L. Miller, Pine City, N. Y., assignor to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application June 10, 1947, Serial No. 753,725

'7 Claims.

1 The present invention relates to an automatic circuit controller, and more particularly to a mechanically operated controlling device for preventing the actuation of an engine starter when a the engine is rotating backward.

The device herein disclosed is allied to the backfire protective devices shown and described in the applications of Kenneth P. Tota, Serial 698,- 162, flied September 20, 1946, and Donald L. Miller, Serial 698,611, filed September 23, 1946, assigned to the assignee of the present invention, wherein a control member engages a moving part of the power plant to be started, and is intended to secure a greater range of travel of the control element, and to provide a particularly simple and economical construction.

adjustment of the mounting means are unneces-.

sary. 1

It is another object to provide such a device which may readily be arranged to secure any desired degree of sensitivity and contact pressure of the circuit controlling means.

It is another object to provide such a device in which single spring means is used to retract the contact-carrying control element and return it to centralized position.

It is another object to provide such a, device which is so arranged that the contact-carrying control element willinvariably engage the moving part with which it cooperates, prior to closure of the starting circuit throughout the entire operative range of adjustment of the device.

It is another object to provide such a device which is arranged to operate equally well in either direction of movement of the engine part, so as to make one model of the device applicable to various types of installation.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. l is a side elevation, partly broken away and in section, of a preferred embodiment of the invention, the electrical circuits thereof being shown diagrammatically;

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1;

Fig. 3 is a top view 0! the device with the cover removed, the parts being shown in cranking position;

Fig. 4 is a view similar to Fig. 3 showing the parts in the positions assumed when the manual control switch of the starting mechanism is closed while the engine is rotating backward;

Fig. 5 is a view similar to Fig. 1 of a. second embodiment of the invention, the parts being shown in idle position;

Fig. 6 is a view similar to Fig. 5 showing the parts in position for causing cranking of the engine;

Fig. 7 is a detail plan view of the control contacts and associated parts, showing the control contacts in closed position as in Fig. 6;

Fig. 8 is a view similar to Fig. 7 showing the,

control contacts opened by backward movement of the engine to be started;

Fig. 9 is a detail in perspective of the link-actuating control lever;

Fig. 10 is a detail plan view partly broken away to show the means for limiting the rotary movement of the control lever about its longitudinal axis; and

Fig. 11 is a detail plan view of an embodiment of the invention arranged to operate in either direction; the electrical system being shown diagrammatically.

In Fig. 1 there is illustrated a starting system for an internal combustion engine including a starting motor SM which is grounded at 'l and connected through a magnetically-operated starting switch 2 to a battery 3 which is grounded at 4 to complete the starting circuit. The magnetic switch 2 includes a solenoid 5, and a control circuit therefor is provided comprising battery 3, a manual switch 6, and a backfire circuit breaker indicated generally by numeral 1 with which the present'invention is mainly concerned. The circuit breaker is connected to the manual switch 6 by a lead 8, and to the solenoid 5 by a lead 9, the solenoid being grounded at l i to complete the control circuit.

As here shown the circuit breaker I comprises a casing l2 having a partition I3 rigidly mounted therein in any suitable manner as indicated at It. A control memberin the form of a lever I5 is pivotally mounted intermediate its ends in an opening in the partition as indicated at it, with its lower end projecting through a slot l'l in the casing l2 whereby the lever is free to rotate around its longitudinal axis, and to swing about an axis perpendicular thereto as indicated by the dotted lines in Fig. 1.

lf'he lower end of the lever II has fixed thereon a control arm l8 here shown in the form of a block of frictional material such as fiber, prefer-v ably attached to the lever by means of a blade I! of elastic material so as to form a yielding connection between the control arm and the lever. The control arm ll extends laterally from the lever in position to be brought into frictional engagement with a moving member 2| of the power plant to be started, such for instance as the fan belt, when the lever I5 is swung into operative position as shown in dotted lines in Fig. l.

The upper end of the control lever l5 has mounted thereon. as indicated at 22, a laterally extending arm 23 preferably in the form ofan elastic blade which is insulated from the lever and carries at its outer end a movable contact 24. Contact 24 is connected by a lead 25 to a binding post 25 mounted in a terminal block of insulating.

material 21, the binding post 26 serving as the attaching. means for the lead 8 of the control circuit.

The terminal block 21 is preferably fixed to the casing l2 by means of a cap 28 fitting the upper end of the casing and having an opening at one end, the edges of which are slidably received in a groove 30 in the edge of the block as shown in Figs. 1 and 2. The cap 28 may conveniently be fixed to the casing by the securing means l4 for partition l3.

A fixed contact in the form of a plate 29 of conductive material is mounted on a block 3| of insulating material which is fixed in any suitable manner to the top of the partition l3. The fixed contact 29 is so located, as best shown in Fig. 2 that when the control lever i5 is in its normal centralized position the movable contact 24 is directly above the fixed contact adjacent one edge the right, thus swinging the control lever It so as to bring the arm l8 thereof into frictional engagement with the side of the fan belt 2| of the engine to be started. If the engine is stationary at this time, the control lever l5 will not rotate around its longitudinal axis, and the contact 24 carried thereby will move straight down so as to engage the fixed contact plate 29 and thereby close the control circuit through leads 32 and I to the solenoid 5 of the starting switch, the control circuit being completed through ground connections H and 4 whereby the starting switch 2 as to cause the arm l8 to rotate the lever II in a thereof, so that if the control lever swings outwardly as shown in dotted lines in Fig. l, themovable contact will engage the fixed contact. Contact 29 is connected by a lead 32 to a second binding post 33 which is also mounted in the terminal block 2! and serves as the, connection for the lead 9 of the control circuit.

Unitary yielding means for normally holding the control lever in retracted centralized position, as shown in Fig. 2, is provided in the form of a spring 34 anchored at 35 and connected by a pin 36 to the lower end of the lever l5. Means under the control of the manual switch 5 for swinging the lever l5 into operative position is provided in the form of a solenoid 37 having a magnetic plunger 38 slidably mounted therein and connected by a pivotally mounted link 39 to the lever l5. Solenoid 31 is attached to the partition l3 by means of a frame M. One end of the solenoid is grounded as indicated at 42, and the other end is connected by a lead 43 to the lead 25, and thereby to the lead 8 of the control circuit.

Means for limiting the pivotal movement of the lever l5 about its longitudinal axis is provided in the form of a pin 44 extending transversely through the lever and arranged to engage the side wall of casing l2, as shown in Figs. 3 and 4, when the lever has rotated through a predetermined angle.

In operation, starting with the parts in normal of idle position as illustrated in full lines in Fig. 1, closure of the manual switch 5 by the operator completes a circuit from the battery 3 through lead 8, binding post 28, leads 25 and 43, to the all) clockwise direction as viewed in Fig. 3 of the drawing whereby the contact 24 remains in engagement with the fixed contact plate 29 and the cranking operation is maintained.

If, however, at the time of closure of the manual switch 5, the engine is rotating backward as a consequence of a backfire or for any other reason, so that the fan belt is moving in the direction of the arrow in Fig. 4, the engagement of the friction arm IS with the fan belt immediately rotates' the lever l5 so as to move the contact 24 in a counterclockwise direction out of engagement with the contact 29, thus preventing closure of the control circuit, whereby the starting motor is maintained deenergized. When the backward movement of the engine ceases it is usually succeeded by a rocking motion in a forward direction which will cause closure of contacts 24, 29 and consequently energization of the starting motor. If this should not take place, it is merely necessary for the operator to open the manual switch 6 thus allowing the spring 34 to return and centralize the lever l5. Reclosure of the manual switch will then cause the starting motor,

to be actuated in the usual manner.

In Figs. 5 to 10 of the drawing there is illustrated an embodiment of the invention which is so arranged that the control contacts are not closed until after the control lever has reached the end of its swinging movement for engagement with the moving part of the engine.

As shown in Fig. 5, a starting motor SM is grounded at 45 and connected by a magnetic starting switch 46 to a battery 41 which is grounded at 48 to complete the starting circuit. The magnetic switch 45 comprises a solenoid 49; and a control circuit therefor is provided comprising the battery 41, manual switch 5|, leads 52 and 53, movable contact 54, fixed contact 55, and lead 55; the control circuit being completed through ground connections 51 and 48.

Circuit breaker mechanism indicated generally by numeral 58 is provided for controlling the 60 contacts 54, 55. As here shown this circuit breaker comprises a generally cylindrical casing 59 having a control lever 6| mounted transversely therein with freedom for rotary movement about its longitudinal axis, and swinging movement so as to bring the arm portion 82 thereof into and out of engagement with a member, such as a fan belt 83 of the power plant to be started. For this solenoid 31 and back to the battery through ground connections 42 and 4. The solenoid is accordingly energized and moves the plunger 38 to is enclosed by a cap 81 of generally rectangular shape, .as best seen in Fig. 10, said cap being secured to the casing by suitable means such as indicated at 68, the pin 66 being arranged to engage the wall of the cap as shown in Fig. in order to limit the pivotal movement of the lever about its longitudinal axis.

The movable contact 54 is mounted on a pin 68 slidably mounted in the control lever 5|, being insulated therefrom as indicated at H, and being yieldably maintained in extended position as shown in Fig. 5 by a spring 12. Fixed contact 55 is in the form of an arcuate plate of conductive material as best shown in Fig. 7, which plate is mounted in any suitable manner on a block 13 of insulating material fixedly attached as indicated at 14 to a cap member 15 mounted on the casing 59 and retained by suitable fastening means A cylindrical terminal supportingmember 11 of suitable insulating material is slidably mounted in the open end of the casing 59 and is provided with a terminal block portion I8 fitting in a cutout portion of the casing and retained therein by the cap 15. Binding posts l8, 8! and 82 are mounted in the terminal block 18; binding post 19 serving for attachment of leads 52 and 53, binding post 8i serving for attachment of the leadv 56 connected to the fixed contact 55, and binding post 82 being grounded as indicated at 83 (Fig. 5).

Means normally urging the control lever Bl toward its idle position is provided in the form of a compression spring 84 located between the lever 5| and the cap 15, the cap being preferably provided with a protuberance 85 for locating the spring. Means responsive to closure of the manvual switch 5| for swinging the lever 6| to bring its arm 62 into frictional engagement with the engine member 63 is provided comprising a solenoid 85 one terminal of which is connected to the control circuit lead 53, and the other terminal connected by a lead 81 to the grounded binding post 82 whereby the solenoid 86 is energized by closure of manual switch 5|. A plunger 88 of magnetic material is slidably mounted in the solenoid 88 and is connected to the lever 6| by a link 89 which is pinned to the plunger as indicated at 9| and has an opening 92 allowing passage of the lever 6| therethrough.

The solenoid 86 is supported in the casing 58 by a frame 93 of magnetic material, the end plate 94 of which forms a guide for the link 88, and an abutment for a cross pin. 95 lnsaid link so as to limit the movement of the link, plunger and lever 6| to the left in Fig. 5 by sure of spring 84.

As best shown in Fig. 9, the opening 82 of link 89 is flattened on one side as shown at 86, and the lever 6| isprovided with a correspondingly flattened portion 51. Thepressure of spring 84 on the lever causes these flattened portions to cooperate when the longitudinal movement of the link 89 is arrested by the pin 95, so'as to rotate the lever 6| back to its normal centered position after it has been displaced therefrom by frictional engagement of r, the arm 62 with th engine member '83 whileit' i's in motion. I

Yielding means normally. holding the movable,

contact 54 onto! engagement with the fixed contact 55 is provided in thetform of a spring 88 anchored to the frame 83 and serving to draw the upper end of the lever tl against'the'left end of the slot 65 in the casing as shown 'inFig. 5. The contacts,- 55 are so arranged'thatthey'cannot come into en agement until'the upper end virtue of the presber -53.

.ol the lever has moved to the right in the slot 8|.

In the operation of this embodiment of the invention and starting with the parts in the positions illustrated in Fig. 5, closure of the manual switch 5! causes energization of the solenoid 85 whereby the plunger 88 moves to the right, swinging the lower end of lever 6| to cause engagement of the arm 82 thereof with the engine mem- When this swinging movement of the lever is thus arrested, further movement of the plunger 88 causes the upper end of the lever 6| to move to the right in the slot 65, thus bringing the contact 54 into engagement with the contact 55 as shown in Fig. 7. The control circuit for the starting switch 451s thereby completed, causing the switch to close and energize the starting motor SM to crank the engine. The consequent movement of the engine member 63 causes the frictional engagement of the arm 62 to rotate thecontrol lever 6| about its longitudinal axis, but since this rotation is in a counterclockwise direction as viewed in Fig. 7, contact 54 maintains its engagement with the arcuatefixed contact 55, and cranking is not interrupted.

If, when the control switch 5| is closed, the engine should be rotating backward for any reason, so that the engine member 63 is moving in the direction of the arrow in Fig. 8, the engagement of the arm 62 of lever 61 causes the lever to be rotated around its longitudinal axis in a clockwise direction to move the contact 54 away from the fixed contact 55. Consequently the subsequent movement of the upper end of lever 8| within slot 65 does not cause closure of the contacts, and untimely actuation of the starting mechanism is prevented.

. In Fig. 11 there is illustrated an embodiment of the invention which is universal in its application in that it is arranged to operate equally well words, if said member is in motion in either direction, the control mechanism willprevent actuation of the starting system.

As there shown, all the parts are the same as those illustrated in Fig. 5 of the drawing and are similarly numbered, with the exception of the fixed contact 55', which is here in the form of a small insert of conductive material in the block 13 of insulation instead of being an arcuate plate as in Fig. 5. With this arrangement, if the engine member 63 is moving in either direction as indicated by the arrows, the engagement of the arm 62 of lever 6| therewith will rotate the lever 5| so as to prevent the movable contact 54 from engaging the fixed contact 55'.

In order to prevent interruption of cranking after initial closure of the starting circuit, due to the opening of contacts 54, 55' by the motion of the engine member 53, a holding resistor I08 is bridged across the contacts 54, 55' by connecting it to the leads 52 and 56 of the control circuit. Resistor Hill has such a value that it will transmit suflicient current from the battery 41 throughthe solenoid 49 to maintain the'starting switch 46 closed, but will not transmit sufllcient current-to cause closure of the starting switch.

In the operation of this embodiment of the invention, if the manual switch 5| is closed at a time when the engine member 63 is stationary, the control circuit will be completed through contacts 54, 55' causing closure of the starting switch 46 and energization of the cranking mechanism. The consequent movement of the engine member i3causes the movable contact 54 to swing out operation is maintained as long as the manual switch BI is closed.

If, however, at the time of closure of the manual switch Ii, the engine member it is moving in either direction, the contact 54 will be swung away from the fixed contact ll thus preventing closure of the control circuit and consequently maintaining the starting mechanism inoperative.

Although certain embodiments of the invention have been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an automatic circuit controller, a lever, means supporting the lever with provision for rotation about its longitudinal axis and swinging movement about an axis perpendicular thereto, a laterally extending control arm at one end of the lever having means for frictionally engaging a movable part, a laterally extending support on the lever carrying an electrical contact; an electrical circuit including a fixed contact adapted to cooperate with the movable contact, means normally holding the lever with its arm disengaged and the contacts open; and means for swinging the lever so as to engage the control arm with th movable part and close the contacts, said fixed contact being so located that pivotal movement of the lever around its longitudinal axis caused by engagement of the control arm with the movable part when it is moving reversely to its normal direction, prevents the movable contact from engaging the fixed contact.

2. An automatic circuit controller as set forth in claim 1 in which the control arm is sufilciently elastic to allow closure of the contacts after engagement of the control arm with the movable part.

3. An automatic circuit controller as set forth in claim 1 in which the means normally holding the lever arm disengaged is in the form of a unitary spring with means connecting it to the lever aranged to move the arm out of engaged position and rotate the lever into centralized position.

4. An automatic circuit controller as set forth in claim' 1 in which the fixed contact is in the form of a plate so located that it maintains engagement with the movable contact when the lever is rotated by movement of the movable part in its normal direction.

5. In a starter control for internal combustion engines, a lever, means for supporting the lever with provision for rotation about its longitudinal axis, and for lateral swinging movement, a latorally extending arm on one end of the lever havin: means for frictlonally engaging a movable part of the engine to be started, a laterally extending support on the lever, an electrical contact mounted on said support, means including a fixed contact cooperating with the first-mentioned contact to cause energization of the engine starter when the contacts are closed; means normally holding the lever with its arm disengaged and the contacts open; and means for swinging the lever so as to engage the arm thereof with the engine part and close the contacts, said fixed contact being so located that pivotal movement of the lever around its lonigtudinal axis caused by engagement of the control arm with the engine part when it is moving prevents the movable contact from engaging the fixed contact.

6. A starter control as set forth in claim 5 in which the closure of the contacts is brought about by further lateral movement of the lever after the arm thereof has been moved into engagement with the engine part.

7. A starter control as set forth inciaim 5 in which the closure of the contacts is brought about by further lateral movement of the lever after the arm thereof has been moved into engagement with th engine part, and including further a second yielding means resisting such further movement of the lever.

DONALD L. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 18,897 Devine July 18, 1933 945,215 Geissinger Jan. 11, 1910 1,142,852 Simon June 15, 1915 1,174,352 Richards Mar. 7, i916 1,488,134 Richmond Mar, 25, 1924 1,915,566 Younghusband June 27, 1933 2,070,994 McGrath Feb. 16, 1937 2,211,701 McGrath Aug. 13, 1940 2,297,402 Garber Sept. 29, 1942 2,297,423 Matthias Sept. 29, 1942 2,339,581 Paulson et al. Jan. 18, 1944 2,369,331 Baker Feb. 13, 1945 

